New build - 18W Tremolo (close but no banana)

[George61]

I actually finished a project, a rare occurrence.

Stuff used: The cabinet is from Stage Craft. The chassis, face plate, and transformers are from GDS. The Scumback speaker rules. The can cap is a F&T. All of the axial electrolytic capacitors are BC Components. All of the film capacitors are Jupiter Vintage Tone. This is my first build with Jupiter caps and they seem to be good for this type of amp. The Jupiter capacitors are easy to come by, unlike Sozo, but they are expensive. The pretty pink resistors are Takman REX, the brown resistors are Mills. There is one Xicon cabon film resistor and the PI plate resistors are carbon composition. Most of the hookup wire is Kimber TCSS. This is my first build with Kimber wire. It is easy to strip for Teflon but it doesn't want to stay where you put it. For a mind boggling $3.50 per foot, you can get it in twisted pairs. The ground wires are 14 gage mil-spec Teflon and the buss bar is 14 gage solid.

The all important tubes: The 12AX7 tubes are current production Tungsol. The output tubes are Russian 6P14P. The rectifier is a No-Name brand NOS EZ81.

What I think of the amp: The amp is good but is not as good as the 36W variant of the 18W that I built. First off, the tremolo sucks the big Kahuna but that is what I expected from what I've read. Much to my surprise, I seem to have blocking distortion on either channel with the volume over 8, or the use the technical term - the amp farts out.

Also, much to my surprise, the tremolo channel is better than the normal channel. The tremolo channel, with the tremolo off, has a bright, metallic sound that is not the least bit ice picky. The tremolo channel has character. The normal channel is dull and lifeless compared to the tremolo channel.

The sweet spot: The tremolo channel with the volume at 8 and the tone at 10. With the guitar volume backed down a bit this amp has a bluesy sound that I personally think is superior to any Fender amp that I have used.

The box on top of the amp is a homemade Air Brake.

Link to more pictures: http://s1326.photobucket.com/user/vox43 ... 8%20Watter

Solder on,
George

[billyz]

Nice work.

[George61]

The normal channel on my amp just didn't seem right so I pulled the amp from the chassis to see if I had made a dumb mistake. That is when I discovered that the layout that I used was wrong. The normal channel input jack wiring isn't even close. It doesn't parallel pins 2 and 7 of V1 in high. Also, the normal channel was quite noisy so I added 27K (the only value that I had two of) grid stoppers.

The layout came from 18watt.com. One would think that someone would have posted a comment about the layout and it would have been corrected. 18watt.com caters to the more neophyte amp building and working off of an incorrect layout is a big disservice.

I found this almost interesting. The 18 watt tremolo layout at Ceriatone is the same wrong layout that is at 18watt.com.

Anyway, the amp really sings now and I am really happy with. It seems that has been a renaissance in EL84 amps and to my ear there is a good reason for it.

There are several layouts at 18watt.com. Check them out. I used the Richie's Improved Tremolo layout which is wrong. The one I have named as (Old) is correct.

[martin manning]

That 18W "Improved Tremolo" input wiring is indeed screwed up. The shields on the coax should not be grounded at both ends either; just at the input end.

FWIW, the high-low inputs are different from the usual concept as used by Fender, and not on the original 18W 1953, 1958, and 1974 schematic. In this case it is a single-parallel triode input, where the "high" jack is the parallel configuration.